Electronic device having E-PAC chassis for spatial arrangement of components and cable organization including channel with retaining wall preventing cable from dislodging from an edge connector

ABSTRACT

An electronic device has a chassis configured to hold multiple electronic components in a predefined three-dimensional arrangement whereby some of the electronic components are positioned elevationally above, and overlapping, other electronic components. Each electronic component has an external dimension which falls within a tolerance range between a lower acceptable tolerance limit and an upper acceptable tolerance limit. The chassis has form fitting recesses to receive and hold the electronic components. Each chassis recess is undersized relative to the lower acceptable tolerance limit for the external dimension of an associated electronic component, but the chassis has effective compliant qualities to receive and hold an electronic component even if it has an external dimension at the upper acceptable tolerance limit. The electronic components are interconnected by conductive cables. The chassis has patterned cable channels formed therein to hold and guide the cables through predefined locations within the electronic device between the electronic components.

TECHNICAL FIELD

This invention relates to an electronic device having a chassis formounting multiple electronic components. Particularly, this inventionrelates to an E-PAC (electronic packaging assembly concept) chassis fora heart defibrillator system which provides spatial arrangement ofelectronic components, such as a CRT display monitor and a capacitor, aswell as uniform cable organization.

BACKGROUND OF THE INVENTION

A chassis for an electronic device typically includes a plastic or metalframework mounted within an external housing. Various electroniccomponents that make up the electronic device are attached to theframework. FIG. 1 shows a conventional chassis 12 for a heartdefibrillator system 10. Chassis 12 holds the electronic componentswithin an external housing 14, which includes an upper housing member 16and a lower housing member 18. The primary electronic components ofdefibrillator system 10 are a CRT display monitor 20, a capacitorassembly 22, and a relay 24 which isolates a human patient fromdefibrillator pulse generation circuitry. System 10 also has a circuitboard 26.

Chassis 12 includes an internal monitor frame 30 which is assembled frommany individual brackets. CRT display monitor 20 is mounted to monitorframe 30. Chassis 12 also includes capacitor frame 32 that supportscapacitor assembly 22. Monitor frame 30 and capacitor frame 32 aremounted to housing 14 via screws, bolts, or other fastening elements.Lower housing member 18 is formed with bosses 34 to maintain theappropriate spacing and orientation of the frames and circuit boards atpredefined locations within the housing when the defibrillator system isassembled.

Each of the frame pieces (e.g., monitor frame 30 or capacitor frame 32)are formed of metal or plastic. For a metal chassis, metal sheets arestamped or bent to a desired shape and then treated using a galvanizingprocess. For plastic pieces, the frame parts are injection molded intothe appropriate shape. The frame pieces are then assembled using screws,bolts, welding, rivets, glue, or other fastening techniques to form thechassis.

Once the chassis is assembled, the electronic components are mounted toit. For instance, CRT display monitor 20 is positioned and secured tomonitor frame 30 via four screws at the comers of the monitor. Likewise,the capacitor elements are assembled and mounted to frame 32. Apart fromstructural support, the chassis also lends the dimensional organizationof the electronic components within a three-dimensional space allocatedby housing 14.

To ensure that the electronic components will all fit in the housingspace, the external dimensions of each component must comply with presettolerance ranges. These tolerance ranges account for inherentimperfections in the manufacturing process and dimension variabilitythat tends to occur from one manufacturer to another. Some componentshave larger tolerance ranges than others. For instance, the CRT displaymonitor has a relatively large tolerance range due in part to theinaccuracies associated with molding the glass used in the monitor.

Conventional chassis are designed to accommodate electronic componentsthat fall within the tolerance range. Typically, the chassis isconfigured to accommodate the largest sized components, while providingsome adjustability to handle the smallest sized components. Toaccommodate varying external dimensions of CRT display monitor 20, forexample, monitor 20 is constructed with four U-shaped prongs which arelocated at the four comers of the glass monitor and extend radiallyoutward to be securely mounted to monitor frame 30 via screws. TheU-shaped prongs or "ears" are elongated a sufficient length to accountfor size variances. As a result, the CRT display monitor can be mountedto frame 30 regardless of whether the CRT glass is at the smallestextreme or largest extreme of the established monitor tolerance range.Apart from the CRT monitor, the conventional chassis and fasteningcomponents all have built in error margins which enable the assembly ofimperfect and inconsistently sized electronic components.

As part of the natural product evolution, it is typically a design goalto make electronic devices smaller and more compact. One way to achievethis goal is to make the components themselves smaller. Another commonway to accomplish the goal is to organize the components in aspace-savings arrangement. However, by accounting for the largest sizetolerances in the various components, the overall chassis necessarilyhas buffer margins to ensure that all components will fit in thehousing. A designer is often hard pressed to find a practical way toreduce the size of the chassis, and hence the overall device, whilestill accommodating the various tolerance ranges.

One aspect of this invention is to provide a chassis that organizes theelectronic components in a compact, three-dimensional space withoutsacrificing the practical need to accommodate various tolerance rangesof the electronic components.

After the components are mounted to the chassis, the components areinterconnected with some form of conductive cabling, such as wires,busses, or ribbon cabling. Standard cabling practice is to gather groupsof cables and join them with fasteners (such as wire clips) to formcable bundles that are manually arranged into some convenient,out-of-the-way vacant portion of the housing space. Where ribbon cablingis used, the assembly person simply arranges the cable itself. If a moresophisticated cable management is desired, it is common to positioninternal molded support parts or hooks at prescribed locations. Thecable is fastened to the hooks, point-by-point, and the intermediateportion between adjacent hooks is left dangling. The free portion of thecable has a tendency to move around within the housing. In someelectronic devices, such as a heart defibrillator system, theuncertainty of cable location can undesirably cause excessiveinterference, such as radio frequency interference (RFI). Differentgeometric locations of the internal cables result in different loopareas in the emissions of radio frequencies. These differences have aneffect on the variability of the RFI emissions and may result in greatermargins than that required for regulatory approvals.

Another aspect of this invention is to provide an enhanced technique formanaging cables within an electronic device.

The overall assembly process is time-consuming. One reason is that thereare a fairly large number of parts counting the chassis--which includesindividual frame pieces, screws, nuts, bolts, washers, spacers,etc.--and the components themselves. Another reason is that the assemblyprocess requires time-involved assembly of the chassis, followed by theassembly of each component to the chassis. The process is not conduciveto automation, but instead is practically limited to hand or manualassembly. Apart from assembly, there is an additional review time toensure that each component is properly and securely fastened to thechassis. If a component is improperly mounted, excessive vibration mightresult, potentially causing damage to that component and thosecomponents around it. The prolonged assembly time drives up costs, asdoes the number of individual assembly parts.

Another aspect of this invention is to provide an electronic device thatis easy to assemble, conducive to automated assembly, and is lessexpensive to produce and assemble by virtue of elimination of manyassembly parts.

To eliminate the number of parts associated with conventional metal orplastic frames, a new packaging process known as E-PAC (electronicpackaging assembly concept) has recently been pioneered and introducedin some products by Hewlett-Packard Company. E-PAC is a technique wherethe electronic components are first placed in a protective frame-likefoam material, and then the foam material is inserted into the housing.The foam material is a bumper grade expanded polypropylene (EPP) whichis molded into form-fitting pieces that hold the electronic components.

The general use of E-PAC as a chassis for an electronic device isdescribed in a European Patent Application EP 0 546 211 A1. The E-PACchassis replaces the conventional metal framework. The EuropeanApplication defines a two piece chassis used to hold electroniccomponents in a common computer workstation. Most of the components areheld in a planer arrangement between the two pieces. The use of E-PAC asa chassis is a significant advance because it eliminates many componentparts while still providing a secure, vibration and noise reducingframework within which components are mounted. The E-PAC significantlyreduces assembly time and enables automated assembly. However, furtherenhancements and modifications were not contemplated by the inventors ofEP 0546211 A1 that, if made, could result in additional benefits.

SUMMARY OF THE INVENTION

This invention pertains to an electronic device with an improvedchassis. The electronic device includes first and second electroniccomponents which are interfaced via a conductive cable. Each electroniccomponent has an external dimension which falls within a tolerance rangebetween a lower acceptable tolerance limit and an upper acceptabletolerance limit. The electronic device also includes a chassis havingform-fitting recesses configured to receive and hold the first andsecond electronic components a spaced distance apart. Preferably, thechassis is an E-PAC (electronic packaging assembly concept) chassis thatis formed of expanded polypropylene. Each chassis recess is undersizedrelative to the lower acceptable tolerance limit for the externaldimension of its associated electronic component. However, the chassishas effective compliant qualities to receive and hold the electroniccomponents even in the event that the external dimensions of theelectronic components are at their upper acceptable tolerance limits. Inthis manner, the chassis accounts for size variations in the electroniccomponents.

The chassis holds the first and second electronic components in apredefined three-dimensional arrangement. For instance, the firstelectronic component can be positioned elevationally above, andoverlapping, the second electronic component. In one implementation of aheart defibrillator system, the chassis supports a CRT display monitoralong one longitudinal axis and supports a capacitor elevationallyabove, and overlying, the CRT display monitor along a secondlongitudinal axis that is perpendicular to the first axis. Accordingly,the chassis organizes the electronic components (in this case, the CRTmonitor and capacitor) in a compact, three-dimensional space whileaccommodating the tolerance ranges of the electronic components.

A cable channel is formed in the chassis to hold and guide the cablethrough predefined locations within the electronic device between thefirst and second electronic components. Rather than bundling the cablewires using clips or hooks, the cable wires are inserted into thepre-formed cable channel and held therein by friction. The pre-formedchannel provides uniformity in cable placement within the electronicdevice which thereby reduces the variability of RFI emissions from onemanufactured device to the next.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a conventional heart defibrillator systemhaving a metal chassis.

FIG. 2 is an exploded view of a heart defibrillator system having achassis according to the preferred embodiment of this invention.

FIG. 3 is an isometric view of the chassis of FIG. 2 in an assembledstate, and without the electronic components.

FIG. 4 is a top isometric view of an upper member of the chassis of FIG.2.

FIG. 5 is a bottom isometric view of the upper member of the chassis ofFIG. 2.

FIG. 6 is a top isometric view of a lower member of the chassis of FIG.2.

FIG. 7 is a bottom isometric view of the lower member of the chassis ofFIG. 2. A circuit board is shown mounted in the chassis.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 2 shows an electronic device 50 constructed according to thepreferred embodiment of this invention. For purposes of discussion,electronic device 50 is shown in an exemplary implementation as a heartdefibrillator system. The primary electronic components of thedefibrillator system are a CRT display monitor 52, a capacitor 54, and arelay 56. The defibrillator system also includes a control circuit board58. The operation of the defibrillator of these components areconventional and are not described in detail herein.

Electronic device 50 has a chassis 60 which holds the electroniccomponents within an external housing (not shown, but similar to housing14 shown in FIG. 1). Chassis 60 has three members: a first or uppermember 62, a second or lower member 64, and a third or rear member 66.The upper member 62 has a top outer surface 68, which is also shown inFIG. 4, and an inner surface 70, which is shown more clearly in FIG. 5.Similarly, the chassis lower member 64 has an inner surface 72, which isshown in FIG. 6, and a bottom outer surface 74, which is shown moreclearly in FIG. 7.

When assembled, the inner surfaces 70 and 72 are juxtaposed in facingrelationship with one another. An orientation coupling assembly isprovided to orient and align the upper and lower members for properassembly. In the illustrated embodiment, the orientation couplingassembly comprises projections 76 formed on lower member 64 andcorresponding, complimentary slots or grooves 78 formed in upper member62. During assembly, projections 76 are aligned with correspondinggrooves 78 to ensure proper orientation and alignment of the upper andlower chassis members.

FIG. 3 shows chassis 60 in an assembled state, and without theelectronic components for purposes of illustration. The three chassismembers form a frame unit having form-fitting recesses configured toreceive and hold associated electronic components. For instance, chassis60 includes a monitor cavity or recess 80 formed partly in the innersurface 70 of upper member 62 and partly in the inner surface 72 oflower member 64. The monitor recess 80 extends along a firstlongitudinal axis 82. Chassis 60 further includes a capacitor recess 84formed in the outer surface 68 of upper member 62. Capacitor recess 84is aligned along a second longitudinal axis 86 that is substantiallyperpendicular to the first longitudinal axis 82 of monitor recess 80. Asshown in FIGS. 2, 5, 6, and 7, chassis 60 also includes a relay recess88 formed partly in both inner surfaces of upper and lower members 62and 64. Relay recess 88 is sized to receive and hold relay 56. Chassis60 further includes a circuit board recess 90 formed in the bottom outersurface 74 of lower member 64 to hold circuit board 58.

Each electronic component has an external dimension which falls within atolerance range between a lower acceptable tolerance limit and an upperacceptable tolerance limit. As noted in the Background section of thisdisclosure, some components have larger tolerance ranges than others.For instance, the CRT display monitor and capacitor have a relativelylarge tolerance range due in part to manufacturing inaccuracies. Therecesses formed to hold these components are therefore purposelyundersized relative to the lower acceptable tolerance limit for theexternal dimension of the associated electronic component. For example,monitor recess 80 is formed smaller than the expected smallest externaldimension of the CRT display monitor to ensure that a comparativelysmall CRT display monitor is adequately held in the chassis. However,the chassis has effective compliant qualities to receive and hold anelectronic component even in the event that the external dimension ofthat electronic component is at the upper acceptable tolerance limit.Thus, even if the CRT display monitor is at the large extreme of itstolerance range for external dimensions, the chassis frame unit willaccommodate the large size monitor. In this manner, the chassis accountsfor size variations in the electronic components.

The chassis is preferably an E-PAC (electronic packaging assemblyconcept) chassis that is formed of "bumper grade" expanded polypropylene(EPP). The three chassis members are formed using injection moldingtechniques. More specifically, an EPP-based chassis is produced by firstcreating foamed up polypropylene granules according to a known method toproduce polypropylene beads. The granules contain carbon which ensuresthat the final plastic material has an electric conductivity sufficientto avoid electrostatic charging of the chassis. Then, the beads areblown with a pressure of about 4 bar into a desired form of a chassismember. This step leads to a volume reduction.

In a subsequent step, vacuum is applied to increase the volume and thebeads assume the shape of the form. Next, hot water vapor of about 180°C. is blown in, causing coalescence of the beads at their surfaces(i.e., cross-linkage). After that, the form is opened and the foam partis removed. Finally, the part is tempered. The process for forming anEPP-based chassis is described in more detail in European PatentApplication EP 0 546 211 A1, which is assigned to Hewlett-PackardCompany.

Expanded polypropylene has several advantageous properties which make itsuitable as a plastic material for a chassis design of this invention.For example, expanded polypropylene has high-dimensional stability, andyet is resilient and energy absorbent. This ensures a shock-absorbingmounting of the electronic components in the chassis. For instance, thecustom molded pocket or recess for relay 56 that is formed in thepolypropylene chassis allows for shock and vibration absorption aroundthe electronically delicate relay.

The deformability or resilience of the plastic material can beinfluenced by the density of the material. In an example chassis, thedensity of the polypropylene is in a range of about 60 to 80 grams/literwhich provides both dimensional stability and a good shock-absorbingeffect. A broader density range of 25-80 grams/liter may also be usedfor certain applications. By varying the density, the hardness andshock-absorbing characteristics of the expanded polypropylene can beadjusted to the specific application. As density decreases, the materialbecomes softer, resulting in a better shock-absorbing quality. Anotheradvantage of polypropylene is its temperature stability which isimportant when the components carried by the chassis generate a largeamount of heat. Another advantage of polypropylene is that it can becompletely recycled.

Although most preferred, expanded polypropylene is not the only possibleplastic material having advantageous properties which make it suitablefor use as a chassis according to this invention. Other plasticmaterials with dimensional stability and a certain resilience can alsobe used as the chassis material. The plastic materials ought to bemoldable to form the chassis shape and contour. Alternative materialsare polyurethane or polyethylene, although these materials are not quiteas satisfactory as polypropylene in all respects.

With reference to FIGS. 2, 3, and 5, chassis 60 includes deformable ribs92 about monitor recess 80. Ribs 92 are thin, more compliant projectionswhich deform under pressure from the CRT display monitor 52 to orientand hold the monitor in the appropriate location within monitor recess80. The deformable ribs 92 adjust to the tolerance differences of theCRT display monitor. Upper member 62 also has a cantilevered latchelement 93 that projects out above the capacitor recess 84. Duringassembly, capacitor 54 is inserted down into the recess and snap element93 bends to permit passage of the capacitor. Once the capacitor is movedpast element 93 and positioned in the recess, the latch element 93returns to its pre-bent position to operatively hold the capacitor inits recess 84.

Chassis 60 holds the electronic components in a predefinedthree-dimensional arrangement within a three-dimensional housing space,which has a depth, a width, and a height. The chassis both defines thelocation of the components as well as provides the desired spacingbetween adjacent components. Some of the electronic components overlapwith others within the three-dimensional space. For instance, as shownin FIGS. 2 and 3, capacitor 54 is held within recess 84 elevationallyabove, and overlying, CRT display monitor 52 which is held withinmonitor recess 80. The chassis has separating elements interleavedbetween the capacitor 54 and CRT display monitor 52 to provide theappropriate spacing therebetween.

As a result, the chassis of this invention organizes the electroniccomponents, such as the CRT monitor and capacitor in a compact,three-dimensional space while accommodating the tolerance ranges of theelectronic components. The three-dimensional organization afforded bythe chassis is advantageous over prior art metal frameworks. Forinstance, in a prior art heart defibrillator system, the capacitor ismounted directly on a special circuit board assembly to the side of theCRT display monitor (rather than above it) because this arrangement ismost convenient for the metal chassis framework. Moreover, the internalmetal support elements, as well as screws, clips, bosses, spacers, andother assembly parts, are eliminated and replaced by pre-formed pockets.

The three-dimensionally spaced electronic components are interconnectedwith conductive cabling in the form of wires, busses, ribbon cable, andthe like. As a means for cable management, pre-pattern cable channelsare formed in the chassis to hold and guide the cables throughpredefined locations within the electronic device. For example, withreference to FIG. 7, cable channels 94, 96, 98, and 100 are formed inbottom outer surface 74 of chassis 60 to route cables from circuit board58 to different locations in the electronic device. Some of thechannels, such as channels 94 and 100, are fairly deep. The wirebundles, represented by bundle 101, are inserted down into thesechannels and held therein via friction from the natural compliance ofthe foam walls. It is common for the cables to be connected to circuitboard 58, or an electronic component, via an edge connector. In FIG. 7,edge connectors 102 and 104 are shown. Cable channels 96 and 98 eachinclude a retaining wall 106 and 108, respectively, which prevent thecable from dislodging from the edge connector. When right angleconnectors are used, the retaining walls can prohibit connectors fromcoming loose during shock and vibration.

The cable channels are advantageous over prior art techniques ofbundling the cables using clips or hooks. One advantage is that theformed chassis has the cable channels in the same location from part topart, making assembly more convenient. The pre-formed channels alsoprovide uniformity in cable placement within the electronic device whichreduces the variability of RFI emissions from one manufactured device tothe next. Such channels further eliminate the use of clips, hooks, andthe like, thereby reducing the overall component and assembly costs.

The electronic device of this invention has several benefits. Onebenefit is that the chassis is configured to accommodate electroniccomponents that posses large size tolerance ranges. Another benefit isthat the components are arranged compactly and efficiently within athree-dimensional space to permit reduction in the overall dimensions ofthe electronic device. Additionally, smaller components can be employedsince special sized recesses are formed in the chassis to support thesmaller components, rather than using larger components which assimilatemore easily into metal framework structures. Another benefit is thecable management afforded by the repeatable, molded cable channels.

The electronic device of this invention has been described in thecontext of a heart defibrillator system. However, other example types ofelectronic devices according to this invention include computers, testand measuring devices, spectrum analyzers, multimeters, signal sources,entertainment electronics, household appliances, lightwave testequipment, and analytical chemistry equipment.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structure and method features. Itis to be understood, however, that the invention is not limited to thespecific features described, since the means herein disclosed compriseexemplary forms of putting the invention into effect. The invention is,therefore, claimed in any of its forms or modifications within theproper scope of the appended claims appropriately interpreted inaccordance with the doctrine of equivalents and other applicablejudicial doctrines.

I claim:
 1. An electronic device comprising:first and second electroniccomponents, at least one of the electronic components having an edgeconnector; at least one conductive cable to interface the first andsecond electronic components, the cable being connected to the edgeconnector of said at least one electronic component; and a chassis forholding the electronic components a spaced distance apart, the chassishaving a cable channel formed therein to hold and guide the cablethrough predefined locations within the electronic device between thefirst and second electronic components, the cable channel including aretaining wall to prevent the cable from dislodging from the edgeconnector when said at least one electronic component is held by thechassis.
 2. An electronic device as recited in claim 1 wherein the cablechannel holds the cable via friction.
 3. An electronic device as recitedin claim 1 wherein:the chassis is formed of expanded polypropylene. 4.An electronic device as recited in claim 1 wherein:the chassis holds thefirst and second electronic components in a predefined three-dimensionalarrangement wherein the first electronic component is positionedelevationally above, and overlapping, the second electronic component.5. An electronic device comprising:a plurality of separate electroniccomponents to be arranged within a three-dimensional housing space atleast one of the electronic components having an edge connector; atleast one conductive cable to interface the electronic components, thecable being connected to the edge connector of said at least oneelectronic component, and a chassis configured to hold the electroniccomponents in a predefined three-dimensional arrangement wherein some ofthe electronic components overlap with others of the electriccomponents, the chassis having a retaining wall to prevent the cablefrom dislodging from the edge connector when said at least oneelectronic component is held by the chassis.
 6. An electronic device asrecited in claim 5 wherein:the electronic components comprise a CRTdisplay monitor and a capacitor; and the chassis comprises a lowermember and an upper member formed with a monitor recess for supportingthe CRT display monitor, the upper member supporting the capacitorelevationally above, and overlapping with, the CRT display monitor. 7.An electronic device as recited in claim 5 wherein:the electroniccomponents are interconnected by conductive cables; and the chassisincludes cable channels formed therein to hold and guide the cablesbetween the electronic components through predefined locations withinthe electronic device.
 8. An electronic device comprising:first andsecond electronic components, at least one of the first and secondelectronic components having an edge connector; at least one conductivecable to interface the first and second electronic components; a chassishaving form fitting recesses configured to receive and hold the firstand second electronic components a spaced distance apart in a predefinedthree-dimensional arrangement wherein the first electronic component ispositioned elevationally above, and overlapping, the second electroniccomponent; and a cable channel formed in the chassis to hold and guidethe cable through predefined locations within the electronic devicebetween the first and second electronic components, the cable channelhaving a retaining wall to prevent the cable from dislodging from theedge connector when the electronic component is held by the chassis. 9.An electronic device as recited in claim 8 wherein:the chassis is formedof expanded polypropylene.
 10. An electronic device as recited in claim8 wherein the first electronic component is a capacitor and the secondelectronic component is a CRT display monitor.
 11. An electronic deviceas recited in claim 10 wherein:the chassis includes deformable ribsabout the recess for the CRT display monitor which deform under pressurefrom the CRT display monitor to orient and hold the CRT display monitorin the recess.
 12. An electronic device as recited in claim 8 whereinthe cable channels hold the cable via friction.